Erik Kjos Fonn

• Fonn, Erik K.; Zahl, Joakim Haugane; Kristensen, Bjørn D. & Thomsen, Lotte (2026). Gendered motives for group formidability among children and adults. Nature Human Behaviour. doi: 10.1038/s41562-026-02606-1. Full text in Research Archive Show summary

  Recent decades have seen a surge of research revealing the core, early emerging psychological building blocks for navigating human societies. Yet, how such core motives operate across life, undergirding political ideology, remains unknown. Here we use the same kind of minimal, abstract group stimuli across the lifespan to show that gendered preferences for majority groups manifest among preschoolers and adults alike (but not among preverbal infants) and that they motivate support for sustaining intergroup hierarchies (for example, ethnic persecution, militarism and social welfare opposition) among adults. Preschool (N = 317) boys, but not girls, preferred majority rather than minority members, whereas infants (N = 180) chose randomly between the two. Among adults (N = 3,467), males also liked the majority more than females, and these coalitional preferences correlated robustly with political ideology. These results indicate that gendered motives for intergroup formidability are rooted in earliest childhood once children begin navigating peer relationships independently.

• Fonn, Erik Kjos; Zahl, Joakim Haugane; Kristensen, Bjørn Dahl; Curry, Oliver Scott & Thomsen, Lotte (2026). Infants use physical size, but not prior possession, to predict conflict outcomes, and do not prefer prior possessors over contenders. Evolution and human behavior. ISSN 1090-5138. 47(5). doi: 10.1016/j.evolhumbehav.2026.106952. Full text in Research Archive Show summary

  Ownership is a pervasive feature of human social life, yet its developmental origins remain unknown. One influential proposal is that human ownership psychology is built on an early-developing and evolutionary ancient sensitivity to first possession: Across species, conflicts over resources are often settled in favor of whoever held a resource first. Among humans, individuals who take what others already possess are often devalued as cooperative partners. Here, we focused on the inferences and preferences infants and toddlers form based on first possession. Across six laboratory experiments (N = 227), we found positive Bayesian evidence that 10–18-month-old infants and young toddlers do not expect intruders will defer to first possessors in territorial conflict, and that 10–13-month-old infants do not prefer prior possessors over those who take (or attempt to take) possessions from others by force. In contrast, we found that infants do expect that larger, more physically formidable agents will prevail in territorial conflict, using identical methods. Hence, prior possession alone is not sufficient for shaping infants' expectations and evaluations in dyadic conflict, though physical formidability is.

• Fonn, Erik K; Zahl, Joakim Haugane; Kristensen, Bjørn Dahl & Thomsen, Lotte (2026). If you can’t beat them, join them: Preverbal infants expect novel agents to choose the majority group. Child Development. ISSN 0009-3920. 97(3), p. 868–880. doi: 10.1093/chidev/aacag019. Full text in Research Archive Show summary

  Society is characterized by negotiation of group interests, often favoring stronger majority groups. Preverbal infants expect members of larger coalitions to prevail in concrete conflicts, but it remains unknown if infants parse the social world by ascribing general default coalitional formidability motives to others, even in the absence of intergroup conflict. Here we show that 9–13-month-old Norwegian infants (N = 168, 83 girls, ethnicity unrecorded, data collected 2018–2025) expected an agent to approach the larger of two separate, coordinated groups (Cohen's g = .15-.17). So did North American and Norwegian adults across explicit (N = 1,704, d > .11) and implicit measures (N = 33, Cohen's g = .23). Humans infer third-party group formidability motives across ontogeny.

• Filesi, Flavia; Kristensen, Bjørn Dahl; Fonn, Erik Kjos; Zahl, Joakim Haugane; Massenet, Mathilde & Bryant, Gregory A. [Show all 7 contributors for this article] (2025). Toddlers Use Vocal Cues to Infer Male Dominance Over Females in Right-of-Way Conflict. Proceedings of the Annual Meeting of the Cognitive Science Society. 47, p. 5924–5932. doi: https:/escholarship.org/uc/item/6033h88p. Full text in Research Archive Show summary

  Men hold more power compared to women, a phenomenon that is globally evident and widely documented. Preverbal infants mentally represent social dominance, and by the age of 18 months can distinguish male and female voices and associate them with faces of the corresponding gender. Here, we investigated whether 18- to 24- month-old toddlers (N=48) expected male-voiced agents to prevail over female-voiced ones in a right-of-way conflict. Using a violation-of-expectation paradigm, we found that toddlers looked longest when female-voiced characters prevailed in dominance conflicts, suggesting they expected that male-voiced agents would prevail instead. Acoustic features of male voices that perceptually suggest greater formidability/physical size (i.e., lower fundamental frequency) may account for this effect. Alternatively, vocal indicators of speaker sex might trigger very early conceptualizations about gender and dominance.

• Kristensen, Bjørn Dahl; Fonn, Erik Kjos; Zahl, Joakim Haugane & Thomsen, Lotte (2025). Infants and Toddlers Expect Others Will Shun the Previously Excluded and Instead Approach the Previously Included. Proceedings of the Annual Meeting of the Cognitive Science Society. 47, p. 5895–5903. doi: https:/escholarship.org/uc/item/05f1k5q9. Full text in Research Archive Show summary

  Navigating social affiliation adaptively is a critical task of human life. If parsing the social world into affiliative groups forms a core, generative mechanism of the evolved human mind, even infants may differentiate between minimal depictions of inclusion and exclusion. Furthermore, whether groups include or exclude others may cue their individual value as social partners. If so, infants may expect third-party observers to continue avoiding those others exclude and prefer those they include, further perpetuating discrimination of the already marginalized. Here, we show that 10-18 m.o. infants (n=96) look longer when a neutral observer approaches a novel agent whom an abstract group previously excluded, rather than included, in an animated violation-of-expectation paradigm. We found no effect of participant age. Movements were identical across scenarios, differing only in a delay between the excluded agent and the group. These findings indicate that even infants infer that observed exclusion versus inclusion will generalize to other interactions with new social partners.

• Fonn, Erik Kjos; Zahl, Joakim Haugane & Thomsen, Lotte (2025). Do infants prefer owners over thieves? Proceedings of the Annual Meeting of the Cognitive Science Society. 47, p. 4650–4656. doi: https:/escholarship.org/content/qt73w7z3tp/qt73w7z3tp.pdf. Full text in Research Archive Show summary

  Normative concerns for ownership fundamentally regulate social interaction regarding resources in humans, but little is known about origins of ownership inferences and evaluations tin earliest human development. Here, we ask if normative evaluations of ownership respect are rooted in an early-developing protomoral dispreference for those who violate ownership. Across two studies (N = 66) infants saw puppet shows where an owner was approached by a non-owner who attempted to take the owner's resource. Infants were subsequently allowed to choose between the two puppets. We controlled for the dominance implications of the outcomes of resource competition by systematically varying whether the non-owner or owner prevailed in attaining the resource. Both studies yielded clear Bayesian evidence that infants did not preferentially reach towards either the owner or ownership violator. These results suggest that infants do not hold strong negative evaluations of those who violate ownership.

• Fonn, Erik Kjos; Zahl, Joakim Haugane; Kristensen, Bjørn Dahl; Margoni, Francesco & Thomsen, Lotte (2023). No single notion of cooperation explains when we respect ownership. Behavioral and Brain Sciences. ISSN 0140-525X. 46. doi: 10.1017/S0140525X23001310. Full text in Research Archive Show summary

  Cooperation is fundamentally moderated by the form of relationship between the actors involved, as is normative resource distribution. We argue that possessions are likely treated differently across different types of cooperative relationships. Whereas Boyer's computational model might in principle account for this, the theory would benefit from a specification of how different cooperative contexts can shape the representation of ownership.

• Fonn, Erik Kjos; Zahl, Joakim Haugane & Thomsen, Lotte (2022). The boss is not always right: Norwegian preschoolers do not selectively endorse the testimony of a novel dominant agent. Child Development. ISSN 0009-3920. 93(3), p. 831–844. doi: 10.1111/cdev.13722. Full text in Research Archive Show summary

  Theories of cultural evolution posit that cues of competence-based prestige, rather than formidability-based dominance, should guide culturally transmitted learning, but recent work suggested that French and Kaqchikel Guatamalan preschoolers place their epistemic trust in dominant others. In contrast, this study shows that 249 three- to six-year-olds (116 girls, tested between 2016 and 2018 across metropolitan locations with varying ethnic composition and socioeconomic status) randomly endorsed the word-labels of dominant and subordinate agents in the egalitarian culture of Norway, using stimuli which solicit dominance inferences among infants and manipulating anonymity across studies to control for egalitarian desirability bias. A meta-analysis estimated that 48% endorsed the dominant's testimony. This demonstrates that the tendency to endorse the epistemic claims of dominant individuals does not emerge reliably in early childhood.

View all works in NVA

• Thomsen, Lotte; Fonn, Erik Kjos; Zahl, Joakim Haugane & Kristensen, Bjørn Dahl (2026). Intergroup Formidability Motives Manifest Among Preverbal Infants and Preschoolers and Relate to Adult Political Ideology. Full text in Research Archive
• Zahl, Joakim Haugane; Fonn, Erik Kjos; Kristensen, Bjørn Dahl; Born, Victoria de Leon & Thomsen, Lotte (2026). Return the Favor: Preverbal Infants Represent and Emotionally Value Direct Reciprocity. Full text in Research Archive Show summary

  The distribution of scarce resources, priority rights, help, and care are central dilemmas of human life. Seminal proposals hold that reciprocity is key for the evolution of cooperation among non-kin, and norms of reciprocity permeate human society. Yet, it remains unknown if human infants are prepared to represent and respond appropriately to direct reciprocity prior to extensive socialization. Here we show that preverbal infants (N=340) predict, postdict, and respond emotionally whether novel agents selectively donate scarce resources to former benefactors, triangulating measures of anticipatory-looking, violation-of-expectation, and emotional responses across six experiments. These results indicate that dedicated psychological coordination mechanisms for direct reciprocity form such basic building-blocks of the human mind that they help humans recognize and appropriately navigate reciprocal coordination already from preverbal infancy onwards.

• Brekke, Lars Kolstad; Kristensen, Bjørn Dahl; Fonn, Erik Kjos; Zahl, Joakim Haugane & Thomsen, Lotte (2026). Prior Help and Reciprocity Judgments. Full text in Research Archive
• Fonn, Erik Kjos; Zahl, Joakim Haugane; Kristensen, Bjørn Dahl & Thomsen, Lotte (2026). If you can’t beat them, join them: Preverbal infants expect novel agents to choose the majority group. Full text in Research Archive Show summary

  Society is characterized by the negotiation of group interests, often favoring stronger majority groups. Preverbal infants expect members of larger coalitions to prevail in concrete conflicts, but it remains unknown whether infants parse the social world by ascribing general default coalitional formidability motives to oth- ers, even in the absence of intergroup conflict. Here we show that 9–13-month- old Norwegian infants (N = 97) expected an agent to approach the larger of two separate, coordinated groups (Cohen’s g = .15–.17), directing their anticipatory gaze toward the larger of two groups as a third-party agent began moving to- ward them. Supporting the specificity of this looking pattern to group-choice prediction, the effect did not extend to larger sets of objects (Cohen’s g = −.11, N = 38), nor to larger groups when the third-party agent moved away from the groups rather than approaching them (Cohen’s g = −.05, N = 33). North American and Norwegian adults similarly predicted that a third-party agent would choose the larger group across explicit (N = 1704, d > .11) and implicit measures (N = 33, Cohen’s g = .23). Humans infer third-party group formidability motives across ontogeny.

• Kristensen, Bjørn Dahl; Fonn, Erik Kjos; Zahl, Joakim Haugane & Thomsen, Lotte (2026). Infants and Adults Expect Others to Perpetuate Social Inclusion. Full text in Research Archive
• Filesi, Flavia; Kristensen, Bjørn Dahl; Fonn, Erik Kjos; Zahl, Joakim Haugane; Massenet, Mathilde & Bryant, Gregory A. [Show all 7 contributors for this article] (2025). Toddlers Use Vocal Cues to Infer Male Dominance Over Females in Right-of-Way Conflict. Full text in Research Archive
• Fonn, Erik Kjos; Zahl, Joakim Haugane & Thomsen, Lotte (2025). Do infants prefer owners over thieves? Full text in Research Archive
• Kristensen, Bjørn Dahl; Fonn, Erik Kjos; Zahl, Joakim Haugane & Thomsen, Lotte (2025). Infants and Toddlers Expect Others Will Shun the Previously Excluded and Instead Approach the Previously Included. Full text in Research Archive
• Zahl, Joakim Haugane; Margoni, Francesco; Fonn, Erik Kjos & Thomsen, Lotte (2024). Preschoolers Selectively Invest in Grateful Recipients in a Trust Game. Full text in Research Archive Show summary

  To sustain the evolution of cooperation, individuals must recognize and discriminate against non-cooperators. Trivers (1971) posited that gratitude is part of the reciprocal system, moving individuals to return favors. We hypothesize that displays of gratitude engender trust, thereby increasing benefactors' willingness to invest in individuals who express gratitude, even in the face of the potential risk of not receiving a return on their investment. We tested this by implementing a modified Trust Game for preschoolers. Children aged 4 - 6 decided whether to give candies to grateful, ungrateful, or neutral characters. If the child chose to give candy, the recipient received three additional candies, which could either be retained or shared back with the child, presenting an investment risk - losing their candy or gaining more than if they kept their candy for themselves. Two studies involving Italian (N = 56) and Norwegian (N = 70) preschoolers showed that they preferentially invested in the grateful recipient over ungrateful or neutral characters. No significant difference was observed between ungrateful and neutral characters. This suggests that gratitude signals altruistic intent, fostering trust and promoting further cooperation.

• Kristensen, Bjørn Dahl; Fonn, Erik Kjos; Zahl, Joakim Haugane & Thomsen, Lotte (2024). Preverbal infants differentiate between socially included and excluded agents. Full text in Research Archive
• Fonn, Erik Kjos; Zahl, Joakim Haugane; Kristensen, Bjørn Dahl & Thomsen, Lotte (2024). Ownership as contingent cooperation: Infants expect cooperators but not competitors to respect each other’s possessions. Full text in Research Archive

View all works in NVA